Nanotubes for the Mass Market

Jun 17, 1998

The remarkable properties of carbon nanotubes could lead to a wide range of applications ranging from smog composite materials to
flat panel displays.
However,
research into the
properties of carbon nanotubes has been limited by the
cost of the
materials - $5,
000 a gram - and
a complex manufacturing process.
Charles Howard Olk from General Motors (
Patent 5753088) has now simplified part of the
production process,
which could lead to the
development of a large-scale manufacturing plants.

Carbon nanotubes - which can be thought of as a rolled-up graphite sheet - were discovered in 1991.
One way to produce large quantities of nanotubes is to place two water-cooled carbon electrodes 1mm apart in a vacuum chamber filled with an inert gas such as argon.
A high-current arc between the
electrodes creates nanotubes on the
negative electrode while removing carbon from the
positive electode.
A scraper then pushes the
nanotubes to the
floor of the
chamber at regular intervals.
As the
positive electrode is 'eaten' away by the
process,
one of the
electrodes has to be moved towards the
other to retain the
1 mm gap.
However,
the
need for these moving parts inside the
vacuum chamber increases the
complexity of the
manufacturing process.
Olk overcomes this problem by submerging the
electrodes in a tank filled with liquid
nitrogen or argon,
avoiding the need for a vacuum chamber. Mechanisms for moving the electrodes can be positioned above the tank in the open air,
simplifying the equipment and the production process.